1. Field of the Invention
The present invention relates to a turbocharged internal combustion engine that includes an exhaust gas recirculation (EGR) system.
2. Background Art
The heavy-duty engine business is extremely competitive. Increasing demands are being placed on engine manufacturers to design and build engines that provide better engine performance, improved reliability, and greater durability while meeting more stringent emission and noise requirements. One approach to meet more stringent emission requirements is to utilize an exhaust gas recirculation (EGR) system.
On a conventional turbocharged diesel engine, the intake manifold is at a higher pressure than the exhaust manifold. This relationship results in the best tradeoff among good fuel economy (due to positive pumping work), engine breathing, and turbocharger operation. The problem is that with the intake manifold at a higher pressure than the exhaust manifold, exhaust gases cannot flow into the intake manifold for EGR. Potential solutions for this problem with conventional engines are to either configure the air system so that the exhaust manifold pressure is made higher than the intake manifold pressure, or use a pump to flow EGR. Setting the exhaust manifold pressure higher than intake manifold pressure is bad for fuel economy.
Further background information may be found in U.S. Pat. Nos. 5,611,202; 6,360,732; 6,460,519; and 6,412,279.
For the foregoing reasons, there is a need to address these issues while still allowing EGR to flow.